(CNN) -- Sen. Barack Obama on Wednesday unveiled a plan to create volunteer and service opportunities to help tackle some of the nation's most pressing issues, part of his weeklong focus on patriotism and national service.

Sen. Barack Obama is expected to say President Bush failed to urge Americans to serve their nation after 9/11.

"This won't be a call issued in one speech or one program -- I want this to be a central cause of my presidency," Obama said in a speech at the University of Colorado in Colorado Springs.

"We will ask Americans to serve. We will create new opportunities for Americans to serve. And we will direct that service to our most pressing national challenges."

He added, "When you choose to serve -- whether it's your nation, your community or simply your neighborhood -- you are connected to that fundamental American ideal that we want life, liberty and the pursuit of happiness not just for ourselves, but for all Americans. That's why it's called the American dream."

Obama highlighted his time as a community organizer on Chicago's South Side and his stint heading Project Vote, a group that helped register 150,000 new African-American voters in the Illinois city, according to his campaign.

"I wasn't just helping other people. Through service, I found a community that embraced me; citizenship that was meaningful; the direction I'd been seeking. Through service, I discovered how my own improbable story fit into the larger story of America," he said.

The presumptive Democratic presidential nominee also touched on the "spirit" of service witnessed after the September 11, 2001, attacks and take aim at the Bush administration's failure to capitalize on this opportunity to call Americans to service.

"We were ready to step into the strong current of history and to answer a new call for our country. But the call never came," he said.

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"Instead of a call to service, we were asked to shop. ... Instead of leadership that called us to come together, we got patriotism defined as the property of one party and used as a political wedge ... we ended up going into a war that should have never been authorized and should have never been waged."

Obama also pressed the need to "ease the burden on our troops, while meeting the challenges of the 21st century" -- a plan he hopes will increase ground forces by 65,000 soldiers and 27,000 Marines.

According to Obama's campaign, the service plan will include:

Expanding AmeriCorps to 250,000 slots and doubling the size of the Peace Corps;

Integrating service-learning programs into schools and universities

Providing new service opportunities for working Americans and retirees;

Expanding service initiatives that "engage disadvantaged young people and advance their education";

Expanding the capacity of nonprofit groups to innovate and expand successful programs across the country; and

Sen. John McCain also has touched on national service with a call to action on his campaign Web site.

In a section entitled "A Cause Greater Than Self," the presumptive GOP nominee asks Americans to donate their time to relief efforts -- including helping out in the flood-ravaged areas of Iowa. See more on McCain's plan